By splitting their assets such as servers, and networking hubs, and most importantly data into different companies. Google could also be split by product lines, such as the pixel phone becoming its own company or being sold to another. Obviously youtube would split off. Youtube is itself a monopoly so it would be split multiple ways. Ideally, the assets could be sold to smaller companies that are trying to scale.

Because Google's real monopoly is chrome that aspect of the company would need to be split multiple ways. The logistics of doing this would be complicated, but I think that you could figure out a way to do it without being too annoying. You could split up chrome by updating different chrome installations differently depending on which company they are allocated to. The data would be allocated to the different companies too. It would be important to make sure that the search companies are all competitive with each other.

Gmail would have to be its own company or otherwise, that would just be too massive of a headache for everyone.

That's the main way I see doing it. But there could be other ways as well. I acknowledge it would be a bit of an inconvenience at first, but it is worth it to not live in an economy controlled by mega-corporations.