Typically it is not possible for the average tomato to get “too much†sun; however too much radiant heat can be damaging for these plants. If these plants are exposed to too much heat and humidity, they can stop producing altogether and eventually due.
Tomatoes can and are grown in areas such as Alaska where they are exposed to full daytime sunlight nearly all the time and they are able to grow just fine.
If you find that your tomato plants are starting to curl up and wilt, chances are the problem is not enough water rather than too much sun.