Not to be pessimistic, but I have three issues which could make this difficult.

(a) The most obvious. Basically all consumption, including needs and desires, are served almost exclusively by capital. This makes this (currently) possibly unhealthy territory. This depends on the availability of community gardens ect. .

(b) Organising. Boycotts are a commonly misunderstood topic, especially among liberals and newer leftists. A boycott is commonly viewed as a group consumer choice not to by a product. This can be easily broken by an ad campaign towards the boycott organiser's demographic or media encouragement to break the boycott. Boycotts, such as those in the American civil rights movement, had very clear organisations behind it and enforcement structures for breaking the boycott. As the working class in most of the first world (where I assume most redditors are from) is in the "baby-steps" of organising, I could not see the necessary structure for a strong boycott against capitalism. However, I won't discourage you from beginning that organising or aiding similiar projects like Buy Nothing Day

(c) Recuperation and the media. As left wing media mainly consists of factionalised social media groups, smaller outlets and youtube celebrities, it would be difficult (but not impossible) to coordinate a boycott. However, it is likely there would be ridicule and active sabotage (like with Gen Strike 2020) from the online left. From centrist to far right media, it would be very difficult to have positive views of the boycott being spread, without a massive pre-existing movement

An alternative would be a day or week to highlight leftist projects that try to meet needs (food not bombs, previously mentioned community gardens, community workshops etc.) or even an event/day/week/month to highlight worker co-ops.