How to negotiate a Summer Offer to Fall?

Hi everyone! My situation is that I received and signed an offer from Company A, which is a mid-size financial service company and has a high return offer rate and quite good WLB (mostly remote). I am super grateful for that offer, but also really like the industry that Company B is in (big tech company), as well as the team I interviewed with. I've been told I should be honest with Company B's recruiter and mention the offer I got from Company A, but I'm not sure how to approach this and don't want to risk burning any bridges for the future either. My best solution is to negotiate this with both Company A and B to see whether I can defer any of my summer offers to the fall term. I wasn't expecting the Company B result to come out this late, cuz normally at this point most people have already signed their summer intern offers, so I was really surprised when I heard back this afternoon.

Appreciate for any possible tips or advice on negotiating this kind of situation! TYIA!!!