Well, sustainable is difficult with such a mega event. It is important to look for eco-friendly solutions and/or reusable for public after the games.
But when I (as a German) hear about the x-attempt of Germany for application and how first thoughts of the officials are „no new buildings/stadium/dome for the games, the competitions will be spread all over the country for maximum eco-friendly games“ I think: just don’t waste any time or money on an application, please.
If it stays within one city, spectators can switch and move between different sport events, but if you have decide where you want to watch and then miss everything else… I see empty benches and no great summer feeling like in Paris.
Nice how they already mentioned how the summer games could be moved to winter, so Qatar can buy, I mean host, the games.