The answer lies in the sort of training that you have just completed, and what your aims are (weight loss, gain, maintenance?), which means one size does not fit all!
It also doesn't necessary mean you can go out and chuff down a load of donuts and chocolate. You might be surprised at how few calories are burnt during exercise and don't be fooled by the numbers of calories the treadmill or bike in the gym tell you, they are massively overestimated.
So lets look at a few scenarios, and I will use myself as an example, using my own stats and experience. So unless stated otherwise, all calories burnt are based on a 51 year old 5ft5, 57kg female:
1. You have just come back from a 1hour max yoga or gym session. You lifted some weights, did a good stretch and puffed a little. I would have burnt approx 200kcals in this session, tops.
What would you eat after this one? Not much more than your normal daily intake to be honest. You haven't stressed the body too much or depleted your energy stores significantly, and you're likely to restore your calorie loss easily enough in your usual diet.
2. You have just done a 30 minute HIIT class, where you were literally hanging out of your @rse on each and every interval (and be honest about this). Your heart rate was through the roof and you're now exhausted. I would have burnt around 250kcals during the workout and continue to do so for a short time afterwards due to EPOC.
A banana post-workout would tide me over until lunch or dinner time. Again, the calorie deficit isn't huge and I would most likely regain these lost calories throughout the course of the days food consumption. As its just 30 minutes its not a huge amount of stress on the body either.
3. You have been out for a 1 hour run. I would burn on average 600kcals for a steady paced run of this length and would usually need to eat fairly quickly afterwards. I might have a glass of whole milk, of just time the run so that it's lunchtime where I would get a good mix of carbohydrates and protein to refuel.
Eggs on toast with avocado or spinach is a favourite, or tuna mayo on ricecakes, or a rice salad with chicken, beans, nuts. More recently I've discovered Shashuka, which I will post a recipe of on here later.
4. You exercise for 1.5+ hours, or racing. When you get to exercising and/or racing for longer periods of time, you really need to think about fueling on the go and also making sure you can get a 3:1 carbohydrate:protein inside you within 30 minutes of finishing. A glass of whole milk is a perfect post-training refuel, as it contains exactly that ratio, is cheap and easily accessible. Then consider a proper meal an hour or so later once you have showered, stretched and got home.
I am a great believer in consuming a wide range of fresh, healthy foods and not excluding any food group from the diet (unless medically necessary such as coeliac), so my all-time favourite 'proper' meal after a hard, long training session or race would be a fillet steak with a huge salad, and off course a pudding of some description!
Fuel is one of the most important aspects of recovery after exercise. My first experience of poor fuelling was when I first lived in Australia and started going on long bike rides (2+hours). We would come home and graze all afternoon on bread, snacks, anything we could get our hands on as we were SOOO hungry. That's when we discovered the power of steak as a recovery fuel. We felt sated, and so much better refuelled for the next training session. In fact, my rowing partner Jenny always swore by a good steak, even when she had to get to silly skinny lightweight size!