In ekāsana, generally only one sitting/one meal is taken, but what is allowed depends on the specific vow followed in your Jain tradition.

About mangoes:

• Ripe mango is usually treated as a fruit and may be taken only if your ekāsana rules permit fruits.
• Unripe/green mango is often considered more like a vegetable/raw item, but whether it is allowed still depends on the exact observance.
• If the ekāsana is being followed strictly with temple/guru guidance, then mango may be restricted unless specifically permitted.

So the safest Jain answer is: eat mango only according to the exact ekāsana rules you are observing; otherwise avoid it.

If you want, I can also explain ekāsana rules in simple Jain terms.