Ramban #1 (citing Targum Onkelos): They meant that their desire of the Manna had rendered them hot-natured.

Ramban #2: Since they ate only the Manna, their bodies were dry, because they did not eat anything to moisten them and keep them fresh. ¹

Michtav me'Eliyahu (1, p.17): One truly enjoys something only if he yearned to get it.

Ibn Ezra, Targum Onkelos and Targum Yonasan Targum: It means that, we lack everything ? we have nothing - besides the Manna, which is all that we seee with our eyes (for which we have to look heavenwards ? Ibn Ezra).

Yoma, 75b: It refers to the fact that the Manna was absorbed in their limbs and they did not need to defecate. ¹ How is it possible, they were asking, for a person to imbibe and not excrete, without bursting? ²

Oznayim la'Torah: Because, as long as they were encmped in Midbar Sinai, close to inhabited country, they would purchsse food from the passing merchants, but now that they had moved into the 'great and fearful desert', they hsd no way of obtaining any food other than the Manna. ¹

Rashi: They meant that they ate nothing other than Manna in the morning and Manna in the evening, and they wanted a more varied diet.

Ramban and Targum Yonasan: They meant that they had nothing of their own and that they had to constantly look longingly to Hashem and to rely on Him for their food in the hope that He will grant it to them, ¹ like a pauper who relies on the good graces of the rich people.

Oznayim la'Torah #1: Even though the Manna adopted the taste of any food they fancied, they saw only Manna - and not the food they were eating, and were therefore comparable to a blind man who does not enjoy his food like a man who can see.

Oznayim la'Torah #2: They were complaining that they had to rely on the Manna to fall each day and could never store their food for a long period. ²