I have just spent a week in an all-inclusive resort in Fethiye, Turkey at TUI Sensatori Resort Fethiye (http://www.thomson.co.uk/destinations/europe/turkey/turkey-dalaman/fethiye/hotels/tui-sensatori-resort-fethiye.html). The weather was pure sunshine, with no clouds in the sky and +30C!
The hotel staff were very good at providing vegan food, although at lunch and dinner I had to have my own chef cook roasted vegetables (in tomato sauce normally or lentil soup) for me because the ones in the buffet were cooked in butter (so be warned that even if there are vegetables check if they cook in butter).
On their menus they had symbols of what their food contains (see photo below), which was very handy. I would double check with a chef/staff to make sure, because there was a dessert with apples and melted dark chocolate and the symbols said it was vegan, but when I asked the chef it did contain milk!
One of my favourite desserts was a roasted pumpkin with tahini and walnuts! So amazing I had two portions! One of the nights was Turkish and they had cakes made of hummus-mung beans, normal, spicy, avocado, quinoa, beetroot, broad bean versions! Heaven!
Their gym was also one of the best hotel gyms I have been in! They had a good selection of yoga (including a candlelit yoga with live guitar music), pilates, boot camp classes as well, be warned that the pilates class is hard core although it could be because it was 35C and you are exercising outside with a gorgeous view of the sea!
If you are going to an all-inclusive hotel I would recommend contacting the hotel before hand to let them know you are vegan, and speaking with the chef while you are there.